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DOI: 10.1055/s-0029-1218797
Easier Preparation of 2,6-Di-tert-butylphenyl Derivatives ¹
Publication History
Publication Date:
25 May 2010 (online)
Abstract
Despite steric shielding by the 2,6-di-tert-butylphenyl group (‘super-2,6-xylyl’ = xyl*), inexpensive sodium phenolate (xyl*-ONa) reacts with dimethyl sulfate to produce only xyl*-OCH3 (94%) with complete suppression of the alternative 4-methylation. Reductive cleavage of xyl*-OCH3 by elemental lithium with the help of an electron carrier generates xyl*-Li, which in turn yields xyl*-CO2H (63%). The corresponding 4-methyl-derivatives of these compounds were obtained analogously. The acid chloride xyl*-COCl (77% yield) acylates HalMgCH2R to give only xyl*-COCH3 (86%) or xyl*-COEt (97%). These two ketones react with n-butyllithium (no carbonyl addition) and Cl-PO(OEt)2 to furnish only the enol phosphates xyl*-C(=CH2)OPO(OEt)2 (84%) or xyl*-C(=CHCH3)OPO(OEt)2 (up to 70%), respectively. Only 1,2-elimination occurs when the latter two products are treated with tert-butyllithium, affording xyl*-C≡CH (68%) or xyl*-C≡CMe (88%), respectively.
Key words
acylation - alkynes - deoxygenation - electron transfer - ketones
- 2
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